1. Field of the Invention
This invention relates to IC band-gap voltage references producing a DC output voltage compensated for changes in temperature. More particularly, this invention relates to such voltage references having improved performance, and further to voltage references which may readily be trimmed during manufacture to provide optimum performance characteristics.
2. Description of the Prior Art
A number of different band-gap voltage reference designs have been proposed, and some have gone into extensive use. One particularly successful design is a two-transistor cell such as shown in U.S. Pat. No. Re. 30,596 and U.S. Pat. No. 4,250,445, both issued to the present applicant. Another design, wherein the emitters of a pair of different-current-density transistors are connected together, is described in a paper presented at the 1981 IEEE International Solid-State Circuits Conference. A variation on that design appears in Linear Databook 2, 1988 Edition, published by National Semiconductor Corporation. While these designs have merit, they have not been fully satisfactory in certain respects. It is an object of this invention to avoid problems presented by prior art devices and techniques.
In a pending patent application Ser. No. 178,121 filed on Apr. 6, 1988 by the present inventor, there is disclosed a high performance amplifier employing as its input stage a matched differential pair of transistors. In the last paragraph of the specification of that application, it is suggested that the input matched pair could be replaced by a mismatched pair to develop a proportional-to-absolute-temperature (PTAT) current for a band-gap reference circuit. The preferred embodiment of the present invention to be described hereinbelow is generally of that proposed configuration, and combines the unique amplifier concepts disclosed in that earlier application together with voltage reference elements to provide superior performance characteristics.